1. Field of the Invention
The present invention relates generally to position sensors and more particularly to a novel fiber optic position sensor.
2. Description of Related Art
In order to control the flight altitude of aircraft, control surfaces located on the wings, stabilizer and tail enable the cockpit crew to control various aspects of flight. These control surfaces are controlled through the manipulation of cockpit controls. Basic example of such control surfaces include ailerons, elevator and rudder.
In early aircraft, these control surfaces were connected directly to the cockpit control by cables which were routed throughout the aircraft. As aircraft became increasingly more complex, the number of control surfaces increased, requiring the addition of further cables and the hardware necessary to route such cables. Of course, the addition of cables and hardware disadvantageously adds to the total weight of the aircraft.
More recently, hydraulic lines and actuators were substituted for the cables. Hydraulic systems allowed a further improvement of servo boost being applied to the associated hydraulic actuators to reduce the amount of force needed on the cockpit controls to move the control surfaces. However, as with cable actuated systems, hydraulic actuated control surfaces also require additional hardware that has to be attached to the airframe which adds weight to the aircraft, requiring greater thrust and fuel carrying capabilities. Furthermore, both cable and hydraulic systems require frequent maintenance and upkeep to assure reliability during the flight.
To alleviate the above disadvantages, "fly by wire" systems have been developed for modern aircraft In such systems, the cockpit controls do not directly act on the control surfaces by mechanical or hydraulic means. Instead, an electrical signal is developed as a function of the position of the cockpit control and this signal is transmitted through electrical wiring to an electromechanical or hydraulic actuator near the respective control surface. The actuator then moves the control surface in response to this position to achieve the desired position The position of the control surface must then also be monitored to assure that correct flight attitude is maintained. Typically, a transducer converts spatial information into a an electrical signal, and this signal is transmitted back to the cockpit to activate a display. A flight control computer manages all such incoming signals from the transducers and the displays.
Although such electrical systems are inherently more reliable than mechanical systems, electrical systems are subject to electromagnetic interference (EMI) and electromagnetic pulses (EMP) which may cause erroneous readings from the position sensors located at the control surfaces to be transmitted to the flight control computer. Furthermore, remote electronic position sensors are active devices which require additional wiring and power to be delivered to them increasing the complexity of the aircraft wiring and systems, thereby reducing overall reliability.